Yes, true believers, there's more to ice cream than cruising the freezer aisle at your local grocery. (Bonus points for identifying who calls fans "true believers"!) If you start looking at the various cartons and food trends, lots of terminology comes to light - ice cream, ice milk, gelato, sherbet, sorbet... it's enough to make your head spin. But it all boils down to a few definitions, mainly determined by ingredients and fat content, which may be helpful if you venture out into making your own frozen confections.
Ice Cream - By definition, ice cream is a frozen dairy product with a minimum 10% milk fat content.
Philadelphia Style - This mixture has no eggs in the base. These are quick to put together, but since they have no eggs in the recipe, this kind of ice cream will freeze harder than a custard base. You may see this kind of ice cream referred to as New York or American-style as well.
Custard - This ice cream has a base that has egg yolks or whole eggs in the recipe, and the base is cooked before frozen. The trick with this type of ice cream is to temper the eggs during the cooking process and strain to ensure no cooked egg pieces end up in your ice cream. Custards can also be called French-style ice cream.
Ice Milk - Similar to ice cream, but has less milk fat (3-6%).
Frozen Yogurt - Pretty much what it says it is - sweetened flavored yogurt that has been frozen.
Sherbet - Usually mainly made of fruit/fruit juices, it has a small amount of dairy (1-2% milk fat.)
Sorbet - Another fruity frozen dessert, but contains no dairy at all.
Gelato - There is no legal American benchmark for gelato, so be advised any ice cream or flavored ice can be labelled gelato in the US. The term is Italian and is distinctive from American desserts because it doesn't contain as much air (or "overrun"), therefore a more dense dessert.
Granita - A dessert ice that is more coarse than sorbet. Most granitas are made from fruit juice, but you can find coffee and wine granitas, as well.
Overrun - Overrun is the air that is whipped into the ice cream base as it freezes. The less overrun an ice cream contains, the more dense it is.
Ripen - This is done with homemade ice cream before serving that keeps it from melting so quickly, and take the texture from soft-serve to firm. Simply transfer the ice cream from the machine into an air-tight container and freeze for a few hours before serving.